Ultra info

http://www.ultrarunning.com/

That was me a little less than a year ago.  Did 3 ultras this year, 50k, 50 mi, and 100k.  That 100k was the hardest thing I've ever done.  One of those, "This is the stupidest thing I have ever done.  I will never ever do this again." kind of things.  Upon further reflection and the world's greatest pain killer (known as "time", I loved it!  I might even take a year off from IM next year and just focus on ultras....maybe try my first 100 miler.

Here's another site worth checking out.

http://www.ultrunr.com/

You also might want to check out a couple discussion forums...

Runnersworld has a pretty active forum.  The "Trail Running" and "Ultra Marathons" forums are where you will find the ultra discussions.

You could check out the "Extreme Running" forum at Kickrunners.com .

There's sort of an old-school email-list-based discussion forum of sorts called the ultralist .  I use gmail for the ultralist, and have all emails from the list grouped under a label and automatically archived, so rather than this stuff clogging my inbox I just click on the label and it's more like reading a typical discussion forum.

This book, A Step Beyond ,  is pretty extensive.

You can read a few posts on my blog if you want to see how my initiation into ultrarunning has gone.  Good luck on your journey! 

Perhaps that's an old link or something?  Looks like this one works...

http://www.nttr.org/